English: A table showing the World Health Organization (WHO) influenza pandemic phases. This was cropped from file:FedFluPandemicResponse.png. The original is in the public domain, per the pandemicflu.gov website, and this crop is also released to the public domain. They request that you give attribution.
No new influenza virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals. If present in animals, the risk of human disease is considered to be low.
2
Now new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease.
Pandemic alert period
3
Human infection(s) with a new subtype, but no human-to-human spread, or at most rare instances of spread to a close contact.
4
Small cluster(s) with limited human-to-human transmission but spread is highly localized, suggesting that the virus is not well adapted to humans.
5
Larger cluster(s) but human-to-human spread still localized, suggesting that the virus is becoming increasingly better adapted to humans, but may not yet be fully transmissible (substantial pandemic risk).
Pandemic period
6
Pandemic phase: increased and sustained transmission in general population.
This image is a derivative of a public domain work created by the U.S. Department of Health & Human Services.
{{Information |Description={{en|1=A table showing the World Health Organization (WHO) influenza pandemic phases. This was cropped from file:FedFluPandemicResponse.png. The original is in the public domain, per the pandemicflu.gov website, and this cr